+.y yields a two-element list of the real and imaginary parts of
its argument. For example, +.3j5 is 3 5,
and +.3 is 3 0 .

x+.y is the greatest common divisor of x
and y .If the arguments are boolean (0 or 1),
the functions +. and *. are equivalent to logical or
and and. The function-.similarly restricted
is not.

]y=: i+2*j. i=: i.4
0 1j2 2j4 3j6
+. y
0 0
1 2
2 4
3 6

The greatest common divisor divides both of its
arguments x and y to produce results that have
no common factor, that is, the GCD of the quotients is 1.
Moreover, these quotients represent the fraction x%y in lowest form.
For example: